Wireless energy transfer is a transfer of electrical energy from an energy source to an electrical load without interconnecting wires. Wireless energy transfer is useful in cases where interconnecting wires or physical electric contacts are inconvenient, hazardous, or not plausible. Wireless energy transfer occurs when a transmitting coil generates a magnetic field and a receiving coil is located within that field so that a current is induced at the receiving coil, i.e. a transmitting coil coupled to a receiving coil.
When the transmitting coil couples with the receiving coil, energy from the transmitting coil can be wirelessly transferred to the receiving coil over a distance. While wireless energy transfer is intended to occur between the transmission coil and the receiving coil, when a foreign object, such as an electrically conductive object, that is not part of the wireless energy transfer system is located within the magnetic field emitted from the transmission coil, the object can inadvertently couple with the magnetic field emitted by the transmitting coil and receive at least a portion of the wireless energy transfer.
The foreign object receiving at least a portion of the wireless energy transfer causes energy wastage and a reduction in efficiency. In addition to the energy wastage and reduction in efficiency, coupling of the foreign object with the magnetic field can also cause the foreign object to radiate the received energy in the form of heat. The radiation of heat from the foreign object can damage adjacent devices or pose a safety threat. Object presence detection and interference detection can reduce energy wastage and reduce safety risks.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.